There are known in the art various solutions devised for assisting the wire guide to cross a duct in human body.
So for example in US 2009209900 there is disclosed device and method for opening vascular obstructions. According to this method there is provided a catheter tube capable of inducing vibrations in a wire guide itself. The vibrations are induced by a magnetic field actuating means.
In U.S. Pat. No. 6,007,514 there is described ultrasonic system with path finding wire guide. The system comprises a wire guide coupled to an ultrasonic catheter which is capable of transmitting ultrasonic energy directly to occlusions.
In US 2008172067 there is described steerable ultrasonic catheter which is provided with ultrasound transmission members with increased distal flexibility allowing contact between the wire guide and ultrasonic catheter.
In WO 2008102346 there is described a wire guide system in which the distal portion is bendable ex vivo to introduce and navigate the distal portion into the vasculature of a specific body and while in vivo.
In US 2009192405 there is described intraluminal guidance system using bioelectric impedance to guide elongate transluminal device through an occlusion in a vessel. The system comprises a couple of electrodes to which an electric current is supplied and a voltage drop between the electrodes is measured. One of the electrodes is located on a distal portion of the transluminal device and the second electrode is in electric contact with the patient. The voltage drop is converted into bioelectric impedance and based on its measurement it is possible to determine if the transluminal device is approaching the vessel wall thus permitting to redirect the device away from the vessel wall.
In US 2008147170 there is disclosed medical device for crossing an occlusion in a vessel. The medical device such as a wire guide is provided with plurality of angled slots to increase the lateral flexibility during navigation of the wire guide.
In WO 2008035349 there is disclosed device and method for crossing a vascular occlusion. The device comprises a catheter and a wire guide insertable through the catheter. A hydraulic chamber is provided between the catheter and the occlusion with the liquid therein having an elevated pressure sufficient for creating a pathway for the wire guide.
In WO 2007095498 there is described a wire guide provided with a shaft and with a stylet deployed in a lumen of the shaft such that the stylet is selectively actuatable within the shaft.
In U.S. Pat. No. 4,654,024 there is disclosed a catheter with a heater mounted on its distal end for melting atherosclerotic plaque to clear an obstruction within an artery. A wire guide is inserted into the lumen of the catheter and the catheter is directed into the proper coronary branch by means of the wire guide. The wire guide is advanced until it meets the obstruction. The heater is then operated and the catheter is advanced as the plaque melts. Once a suitable channel has been opened, the catheter is removed and a conventional balloon dilatation catheter is slid over the wire guide.
In U.S. Pat. No. 5,350,375 there is disclosed a catheter with laser induced fluorescence intensity feedback and control during laser angioplasty. The catheter includes an eccentric wire guide lumen and at least one optical fiber positioned relative to an obstruction in a blood vessel with possibility for rotating the catheter and monitoring the fluorescence intensity. When the fluorescence intensity has a maximum value, the optical fiber is aligned with the obstruction. The fluorescence intensity feedback is used to determine when a laser ablation device has crossed an occlusion. An abrupt drop in fluorescence intensity indicates that the ablation device has crossed the occlusion.
The known in the art solutions may be arbitrary divided into two main groups.
The first group includes solutions intended merely for assisting the crossing of obstructed duct by improving flexibility of the wire guide without however disrupting the obstruction occurred in the duct.
The second group includes solutions intended for disruption by applying energy to the obstruction while the energy is induced either in the wire guide itself or in an auxiliary catheter or probe accompanying the wire guide during its advancement along the duct. Among those methods one can mention ultra-sound, hydraulic, laser, and other methods.
On the other hand there are known in the art medical lithotriptors which operation is based on so-called electro-impulse principle.
This principle was adopted from mining technology, where it has been used for so-called high-power electro-impulse destruction of materials. This principle is based on applying of electrical impulses with the rise time of not more than 500 nanoseconds to two electrodes positioned on a solid mineral material immersed in dielectric liquid or liquid medium with relatively small conductivity. The applying of such impulses is associated with producing discharge, which does not propagate through the surrounding liquid medium, but rather through the bulk of the solid body itself.
The electro-impulse technology was developed in late fifties in Russia and since then it was successfully implemented in such fields like crushing and disintegration of hard rocks and ores in mining industry, destructing of concrete blocks in building industry, drilling of frozen ground and extremely hard rocks, crushing of various inorganic materials, etc.
A survey of this technology can be found in a monograph “Basics of electro-impulse destroying of materials”, by Semkin et at. Saint-Petersburg, Nauka, 1993.
According to this technology two or more electrodes are placed immediate on the surface of a solid body (rock) and very short impulses of voltage U (t) are sent through them. Once an electrical breakdown between the electrodes is initiated, it occurs in the bulk of the solid body and is associated with producing of the breakdown discharge channel that extends within the bulk of the body.
The body itself serves as a medium to promote propagation of the electrical breakdown rather than the surrounding medium. Extension of the discharge channel through the body is accompanied by mechanical stresses, which stretch the body and destroy it as soon as tensile strength of the body is exceeded.
In fact in the process of electro-impulse destroying the initiation and propagation of the discharge is similar to a micro-explosion within the body.
It can be readily appreciated that since tensile strength of a rock is at least an order of magnitude less than its compressive strength, the electro-impulse crushing is associated with consumption of much less energy, than conventional electro-hydraulic crushing.
It has been also empirically established, that the probability of propagation of the breakdown channel through the body is higher when a very short voltage impulses are applied to electrodes, positioned on a solid body immersed in a liquid medium, since the voltage required for the breakdown within the bulk of the body is less, than the voltage required for breakdown within the liquid medium outside of the body.
Despite the fact that this technology exists for more than 40 years it has been employed mainly in mining and building industry for destruction of very large objects like rocks or concrete blocks as e.g. disclosed in International publication WO 9710058.
The electro-impulse technology was only recently employed in medicine for lithotripsy treatment of calculi and a lithotriptor implementing this technology has been devised. This lithotriptor is manufactured by the company Lithotech Medical Ltd., Israel and is commercially available for urology procedures, under the name “Urolit”. The method and apparatus for electro-impulse lithotripsy is disclosed in International application PCT/IL03/00191.
Thus one can conclude that the problem of passing a wire guide through an occluded duct is known for a long time and there exist many attempts to solve it. Nevertheless there is still a room for a new solution. This new solution could beneficially combine advantages of electro-impulse disrupting along with imparting to auxiliary catheter high flexibility and maneuverability during advancement thereof through occluded duct.